Pic makes first of many winking allusions to “Risky Business” very early, as soundtrack swells with Tangerine Dream-like sound while Matthew Kidman (Hirsch) notes shapely blond Danielle (Cuthbert) moving into the suburban home next to his. Later that evening, he “accidentally” sees her while she disrobes in front of an open window. Before things get too steamily kinky, however, pic turns playfully raunchy: Danielle spies Matthew spying her, and retaliates by forcing him to become a very reluctant streaker on a nearby moonlit street. Chalk it up as just another way of “meeting cute.”

Quickly recovering from his humiliation, Matthew — a straight-arrow student with political ambitions — begins a tentative courtship of Danielle, who’s not entirely averse to his attentions. (Evidently, they’re roughly the same age.)

A half-hour in, however, he learns that she’s not nearly as innocent as she seems: Danielle is a porn actress who only recently retired from her trade. Matthew is shocked — and, briefly, more than a little turned on. But he vows to remain her new best friend, even if that means he’ll have less time to prepare for a Georgetown U. scholarship competition.

Working from a shamelessly derivative script by Stuart Blumberg, David T. Wagner and Brent Goldberg, director Luke Greenfield (“The Animal”) keeps “Girl” loping from scene to scene with little regard for pace, plausibility or tonal consistency. To his credit, however, he does surround the attractive but bland leads with first-class supporting players.

Timothy Olyphant strikes an impressively deft balance of hearty amiability and understated menace in his scene-stealing turn as Kelly, Danielle’s exuberantly sleazy former producer, who’s implacably determined to talk his star into a comeback. It’s never entirely clear whether Kelly is a charming rogue or a brutal thug (or maybe a slightly more benign version of the “killer pimp” essayed by Joe Pantoliano in “Risky Business”). Ambiguity of the character provides dramatic tension sorely missing whenever Olyphnat is off screen.

In far more conventional supporting roles — the hero’s high school buddies — Paul Dano is aptly uptight as nerdy Klitz, while Chris Marquette is at once amusingly crass and seriously careerist as Eli, a would-be filmmaker who figures prominently in pic’s climax. Modestly clever final twist is one of pic’s funniest variations on key “Risky Business” plot elements.

Tech values are mostly unremarkable, though soundtrack offers an unusually tasty mix of pop tunes from past four decades. Harry Nilsson’s “Jump Into the Fire” and Donovan’s “Atlantis” are put to especially shrewd use.

For the record: Pic has no direct relationship to Christine Fugate’s “The Girl Next Door,” well-received 1999 docu about housewife-tuned-porn star Stacy Valentine.